The development of spermatogonia includes a characteristic sequence of events culminating with the formation of a highly complex differentiated cell -- a spermatozoon. The molecular processes involved in the germ cell determination and differentiation are not well understood. The appearance of testis-specific histones during mammalian spermatogenesis suggests that these proteins may have important role in the germ cell differentiation. The proposed studies involve isolation and purification of testis-specific basic proteins and their variants. The purified proteins will be biochemically characterized and used to generate specific antibodies in the rabbits. These specific antibodies will be utilized for the localization and quantitative estimation of the individual proteins. The specific antisera will be also used to isolate histone-specific mRNA's from the spermatogenic cells. The specific mRNA's will be utilized for the synthesis of cDNA probes which could in turn be used to probe the regulatory aspects of the testis-specific proteins. In addition, the biosynthetic aspects of the testis-specific basic proteins will be investigated by in vivo labeling and radioimmunoassay.